Your car’s air conditioner is an important accessory – it helps keep you and your passengers comfortable and safe during hot weather. However, it’s operated by your engine and places an additional load on your engine when it’s running. That means it increases your fuel expenditure (decreases your fuel economy). How much does it affect your fuel mileage? The answer is: a lot.
How much will my fuel mileage be affected?
Note that there is no single answer to this question, as there are a number of different factors in play. The actual temperature outside will have an effect, as will the size of your engine, the make and model of your car, the condition of your air conditioning system and many others. However, the US EPA notes that running the air conditioner in very hot weather can increase your fuel consumption by up to 25%, and that the effect of using the AC in a hybrid or electric vehicle can be even greater.
The best defense against decreasing fuel economy is actually pretty simple – use your windows at lower speeds, and turn on the air when you hit the highway. Of course, open windows increase drag, which also reduces fuel economy, but the impact isn’t as great as running the AC at lower speeds.
Ensuring that your air conditioning system and engine are properly maintained will also help improve your fuel economy. Regular oil changes and clean air filters can do a great deal to improve your fuel mileage. Ensuring that your AC system has the right level of refrigerant is also an important consideration here.